Pressure-sensitive recording sheet with microcapsules having polyurea walls

ABSTRACT

A pressure-sensitive recording sheet having reduced color fog which comprises a base sheet and (1) a layer of microcapsules containing a color former in oil droplets surrounded by the wall of a polyurea obtained by the reaction of a polyisocyanate or isocyanate-containing polyisocyanate adduct with a polyamine or polyamine adduct, and (2) a layer of an adsorbent or color reactive substance capable of producing a distinct color upon contact with the color former. Layers (1) and (2) are applied to the same surface of the base material.



1. A PRESSURE-SENSITIVE RECORDING SHEET WHICH COMPRISES A BASE MATERIAL AND (1) A LAYER OF A COLORLESS OR SUBSTANTIALLY COLORLESS COLOR-FORMING SUBSTANCE RENDERED COLORED UPON REACTION WITH A DEVELOPER, ENCAPSULATED IN WALLS OF A POLYUREA OBTAINED BY THE REACTION OF A POLYISOCYANATE OR ISOCYANATECONTAINING POLYISOCYANATE ADDUCT WITH A POLYAMINE OR POLYAMINE ADUCT, AND (2) A LAYER OF DEVELOPER CAPABLE OF GIVING A COLORED SUBSTANCE BY REACTION WITH SAID COLOR-FORMING SUBSTANCE, LAYERS (1) AND (2) BEING ON THE SAME SURFACE OF SAID BASE MATERIAL.
 2. The pressure-sensitive recording sheet of claim 1, wherein said isocyanate-containing polyisocyanate adduct is an adduct formed between a polyisocyanate and a compound containing a hydrophilic group.
 3. The pressure-sensitive recording sheet of claim 2, wherein said compound containing a hydrophilic group is selected from the group consisting of polyamines, polycarboxylic acids, polyols, polythiols, polyhydroxy compounds and epoxy compounds.
 4. The pressure-sensitive recording sheet of claim 1, wherein said polyamine adduct is an adduct formed between a polyamine and an epoxy compound.
 5. The pressure-sensitive recording sheet of claim 1, wherein the polyurea is obtained from an isocyanate containing polyisocyanate adduct which has at least two uncombined isocyanate groups.
 6. The pressure-sensitive recording sheet of claim 1, wherein the polyurea is obtained from a polyamine adduct which has at least two uncombined amine groups.
 7. The pressure-sensitive recording sheet of claim 1, wherein the polyisocyanate is selected from the group consisting of dithioisocyanates, diisocyanates and triisocyanates.
 8. The pressure-sensitive recording sheet of claim 1, wherein the polyisocyanate is a polyisocyanate monomer.
 9. The pressure-sensitive recording sheet of claim 1, wherein the polyisocyanate per se or polyisocyanate used to form the adduct is selected from the group consisting of m-phenylene diisocyanate, p-phenylene diisocyanate, 2,6-tolylene diisocyanate, 2,4-tolylene diisocyanate, naphthalene-1,4-diisocyanate, diphenylmethane-4,4''-diisocyanate, 3,3''-dimethoxy-4,4''-biphenyl-diisocyanate, 3,3''-dimethyl diphenylmethane-4,4''-diisocyanate, xylylene-1,4-diisocyanate, xylylene-1,3-diisocyanate, 4,4''-diphenylpropane diisocyanate, trimethylene diisocyanata, hexamethylene diisocyanate, propylene-1,2-diisocyanate, butylene-1,2-diisocyanate, ethylidine diisocyanate, cyclohexylene-1,2-diisocyanate, cyclohexylene-1,4-diisocyanate, xylylene-1,4-diisothiocyanate, ethylidinne diisothiocyanate, hexamethylene dithioisocyanate, 4,4'',4''''-triphenylmethane triisocyanate, toluene-2,4,6-triisocyanate, polymethylene polyphenyl isocyanate, and 4,4''-dimethyldiphenyl methane-2,2'',5, 5''-tetraisocyanate.
 10. The pressure-sensitive recording sheet of claim 1, wherein the polyamine per se or polyamine used to form the adduct is an aromatic amine having at least two free amino groups in the molecule.
 11. The pressure-sensitive recording sheet of claim 1, wherein the polyamine per se or polyamine used to form the adduct is an aliphatic amine having at least two free amino groups in the molecule.
 12. The pressure-sensitive recording sheet of claim 1, wherein the polyurea is obtained from a polyamine per se or the polyamine used to form the adduct is selected from the group consisting of o-phenylene diamine, p-phenylene diamine, diamino naphthalene, 1, 1,3-propylene napthalene or hexymethylene diamine.
 13. The pressure-sensitive recording sheet of claim 1, wherein a polyisocyanate is reacted with the polyamine or the polyamine adduct.
 14. The pressure-sensitive recording sheet of claim 1, wherein a isocyanate-containing polyisocyanate adduct is reacted with the polyamine or polyamine adduct.
 15. The pressure-sensitive recording sheet of claim 1, wherein a polyamine is reacted with the polyisocyanate or the isocyanate-containing polyisocyanate adduct.
 16. The pressure-sensitive recording sheet of claim 1, wherein a polyamine adduct is reacted with the polyisocyanate or isocyanate-containing polyisocyanate adduct.
 17. The pressure-sensitive recording sheet of claim 3, wherein the compound is a polyamine.
 18. The pressure-sensitive recording sheet of claim 3, wherein the compound is a polycarboxylic acid.
 19. The pressure-sensitive recording sheet of claim 3, wherein the compound is a polythiol.
 20. The pressure-sensitive recording sheet of claim 3, wherein the compound is a polyhydroxy compound.
 21. The pressure-sensitive recording sheet of claim 3, wherein the compound is an epoxy compound.
 22. The pressure-sensitive recording sheet of claim 3, wherein the compound is a polyol.
 23. Pressure sensitive microcapsules containing a colorless color forming substance in an oily liquid encapsulated in walls of a polyurea produced by the reaction of a polyisocyanate or isocyanate-containing polyisocyanate adduct with a polyamine or polyamine adduct comprising: a. dissolving the polyisocyanate or isocyanate-containing polyisocyanate adduct in the oily liquid having dissolved therein the color forming substance; b. emulsifying the product of step (a) in a polar liquid; c. adding to the product of step (b) the polyamine or polyamine adduct; and d. subjecting the system of step (c) to polymerization conditions, whereby the oily liquid having dissolved therein the color forming substance is encapsulated in the polyurea product formed. 